M4R is a filename extension for AAC format, which is developed by Apple Inc. It is typically used to save custom iPhone ringtones from Apple iTunes. M4R can only be created from iTunes purchased songs and is usually DRM protected. It can open on iTunes, VLC Media Player, Apple QuickTime Player, and more.
DV (Digital Video) is a file created using a digital format and saved as raw data. A DV file contains 80-byte DIFs (Digital Interface Blocks), with each block having video, audio, and metadata. DVD files use lossy compression for videos, while sounds stay uncompressed. And although it was originally meant for tape recording, DV can also save data on hard disc drives and optical discs.
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